pinctrl: bcm2835: Fix memory leak in error path

In case of an invalid pin value bcm2835_pctl_dt_node_to_map()
would leak the pull configs of already assigned pins.
So avoid this by calling the free map function in error case.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Fixes: e1b2dc70

 ("pinctrl: add bcm2835 driver")
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>